The success of the home-made bomb

"The investigation into the Islamist cell that blitzed London on July 7, 2005 was unable to establish whether its members had acquired their lethal know-how through the internet. One of them had received explosives training in Pakistan and may simply have passed on his expertise. "My feeling is that they were among the last generation of UK terrorists who could relatively easily arrange for hands-on training abroad," says one British terrorism expert. "Security is so tight now, our own wannabe jihadists are almost certainly turning to the web.":A good deal of the extremist material on the internet is fairly basic, says an Israeli analyst who monitors online terrorism, "but if you know where to look, there are some very scary sites providing step-by-step guides to making and detonating a powerful IED".

One that he singled out, requesting its name was not published, had a video produced by an Iraqi extremist group that showed how to prepare an IED for use in a roadside ambush. As martial music blares, there is a detailed demonstration of how to attach the detonator to a bomb composed of two artillery rounds. The scene then shifts to a dusty track where the camera shows the bomb – to be set off by a command wire – being dug into a roadside verge.

When a pair of tanks come grinding past the ambush point, there is a blinding flash and a huge explosion, followed by exultant cries of "Allahu akbar" – "God is great". A message in Arabic claims that one of the tanks was destroyed. Half an hour later the dramatic footage was available on the internet. "The insurgents understand very well the power of such images as a recruiting tool," Metz acknowledges. "A huge, smoke-filled explosion that leaves a gaping crater in the road is far more impressive than a simple bang.""

"To borrow The Economist's apt phrase, "jihad's open university" is flourishing in cyberspace"